For example, as illustrated in FIG. 3, a medium/large-capacity uninterruptible power supply (called UPS) apparatus 1 has a configuration in which a plurality of power supply units 3 (3a to 3n) is stacked vertically and detachably mounted on a rack body 2 of a so-called 19 inch size in conformity with the EIA standard. Specifically, for example, the UPS apparatus 1 of 100 kVA is built with five power supply units 3 (3a to 3n) of 20 kVA being mounted on the rack body 2. Furthermore, Reference Numeral 4 of the drawing indicates a control unit which controls the operation of the power supply units 3 (3a to 3n). Reference Numeral 5 indicates an input/output unit which is connected to a power supply line drawn from a system power supply (not illustrated) and a power supply line connected to load equipment (not illustrated).
In addition, the case unit comprising the power supply units 3 (3a to 3n) and the control unit 4 respectively has a configuration that an electric apparatus body such as an electric power converter or a control device is accommodated in a box-shaped case 11 of a 4 U size having a height of 7 inch (approximately 179 mm). The 4 U size indicates the size of the case unit four times the size of a basic unit having a height of 1.75 inch (approximately 44.45 mm). These case units are mounted on or detached from the rack body 2 through the front side of the rack body 2 as illustrated in FIG. 3.
Here, the power supply units 3 (3a to 3n) illustrated in FIG. 3 have, for example, a configuration that a plurality of cooling fans 12 is provided in the front surface of the case 11 so as to forcedly cool a power semiconductor device, etc. in the electric power converter accommodated in the case 11. Further, in each rear surface of the power supply units 3 (3a to 3n), plug-in connectors 13 are provided at both sides of the rear surface of the case 11, for example, as illustrated in FIG. 4.
Those plug-in connectors 13 are connected to connectors (not illustrated) provided in the inner area of the rack body 2 when the power supply units 3 (3a to 3n) are mounted on the rack body 2, and are disconnected from the connectors when the power supply units are detached from the rack body 2. By adopting such a connector structure, the electric connection of the power supply units 3 (3a to 3n) to the rack body 2, and further, the electric connection among the units 3 (3a to 3n), the control unit 4 and the input/output unit 5 is automatically performed only by mounting the power supply units 3 (3a to 3n) on the rack body 2. Here, the electric connection indicates the connection of the power supply lines and the connection of various control signal lines.
Incidentally, when maintenance or the like is performed by separating the power supply units 3 (3a to 3n) from the rack body 2, there is a need to stop the operation of the power supply unit 3a (3b to 3n) by separating the power supply units 3a (3b to 3n) from the rack body so as to interrupt the supply of electric power to the power supply unit. If the power supply unit 3a (or 3b to 3n) is separated from the rack body 2 in the operation state, a problem arises in that a high-voltage spark discharge occurs between the plug-in connector 13 and the connector portion due to so-called hot swapping. As a result, in many cases, such power supply units 3 (3a to 3n) are equipped with an interlocking mechanism which allows the operation of the power supply units 3 (3a to 3n) only when the power supply units are mounted on the rack body 2.
Hitherto, such an interlocking mechanism has been represented as, for example, a switching gear with a shutoff switch, and the interlocking mechanism is configured such that the interlocking state is released only by intentionally sliding a sliding plate biased by a spring. Such an interlocking mechanism is specifically disclosed in, for example, Patent Document 1. Further, for example, Patent Document 2 discloses a device in which a case unit is mounted on rack body. Here, a front surface of the case unit is provided with a sliding plate which covers a fixed screw fixing the case unit to the rack body, and hence the unintentional separation of the fixed screw is prevented.
Specifically, in the interlocking mechanism illustrated in Patent Document 2, an operation lever of a power switch provided in the front surface of the case unit is turned on only when the sliding plate is moved to a position where the fixed screw is covered. Then, the sliding of the sliding plate is allowed only when the operation lever is set to an off position, and the fixed screw is exposed so that the fixed screw may be separated. Then, the case unit may be mounted on or separated from the rack body only when the power switch of the case unit is turned off.